docs: document public modules

lib/protox/encode.ex

@@ -1,7 +1,5 @@
 defmodule Protox.Encode do
-  @moduledoc """
-  This module contains the functions necessary to encode protobuf messages.
-  """
+  @moduledoc false
 
   use Protox.{
     Float,

lib/protox/kind.ex

@@ -1,41 +1,15 @@
-defmodule Protox.Scalar do
-  @moduledoc false
-
-  @typedoc """
-  All the possible types that can be used as a default value for a scalar.
-  """
-  @type scalar_default_value_type ::
-          binary()
-          | boolean()
-          | integer()
-          | float()
-          | atom()
-          | nil
-
-  @type t() :: %__MODULE__{
-          default_value: scalar_default_value_type()
-        }
-
-  @enforce_keys [:default_value]
-  defstruct [:default_value]
-end
-
-defmodule Protox.OneOf do
-  @moduledoc false
-
-  @type t() :: %__MODULE__{
-          parent: atom()
-        }
-
-  @enforce_keys [:parent]
-  defstruct [:parent]
-end
-
 defmodule Protox.Kind do
-  @moduledoc false
+  @moduledoc """
+  Defines the kind of a field.
+
+  It can be one of the following:
 
-  @typedoc """
-  This type indicates how a field is encoded.
+  - `Protox.Scalar` - A [scalar](https://protobuf.dev/programming-guides/proto3/#scalar) value.
+  - `:packed` - A [packed repeated](https://protobuf.dev/programming-guides/encoding/#packed) field.
+  - `:unpacked` - An [unpacked repeated](https://protobuf.dev/programming-guides/encoding/#optional) field.
+  - `:map` - A [map](https://protobuf.dev/programming-guides/encoding/#maps) field.
+  - `Protox.OneOf` - A [oneof](https://protobuf.dev/programming-guides/encoding/#oneofs) field.
   """
+
   @type t() :: Protox.Scalar.t() | :packed | :unpacked | :map | Protox.OneOf.t()
 end

lib/protox/message_schema.ex

@@ -1,6 +1,17 @@
 defmodule Protox.MessageSchema do
-  @moduledoc false
+  @moduledoc """
+  Represents the schema of a Protocol Buffers message once it has been processed by Protox.
 
+  This struct contains all the necessary information to describe a message in a Protocol Buffers
+  schema, including its name, syntax version, fields, and optional file-level options.
+
+  ## Fields
+
+  * `:name` - The atom representing the name of the message
+  * `:syntax` - The Protocol Buffers syntax version (e.g., `:proto2` or `:proto3`)
+  * `:fields` - A map of field names to their definitions (`Protox.Field.t()`)
+  * `:file_options` - Optional file-level options, represented as a map if any.
+  """
   @type t() :: %__MODULE__{
           name: atom(),
           syntax: atom(),

lib/protox/one_of.ex

@@ -0,0 +1,20 @@
+defmodule Protox.OneOf do
+  @moduledoc """
+  Represents a [oneof field](https://protobuf.dev/programming-guides/proto3/#oneof) in protobuf.
+
+  A oneof field represents a group of fields where only one of them can be set at a time.
+  This module provides a struct to store the parent field of this oneof group, that is, the
+  field that effectively contains the set value.
+
+  ## Fields
+
+  * `:parent` - The name the parent field of this oneof group.
+  """
+
+  @type t() :: %__MODULE__{
+          parent: atom()
+        }
+
+  @enforce_keys [:parent]
+  defstruct [:parent]
+end

lib/protox/scalar.ex

@@ -0,0 +1,29 @@
+defmodule Protox.Scalar do
+  @moduledoc """
+  Represents a scalar field in a Protocol Buffer message.
+
+  This module defines a struct that holds information about a scalar field,
+  particularly its default value. Scalar fields are the basic data types
+  such as integers, floats, booleans, strings.
+
+  The default value is used when a field is not present in the encoded message.
+  """
+
+  @typedoc """
+  All the possible types that can be used as a default value for a scalar.
+  """
+  @type scalar_default_value_type ::
+          binary()
+          | boolean()
+          | integer()
+          | float()
+          | atom()
+          | nil
+
+  @type t() :: %__MODULE__{
+          default_value: scalar_default_value_type()
+        }
+
+  @enforce_keys [:default_value]
+  defstruct [:default_value]
+end